As a pump for circulating and transporting chemical liquid in various processes such as washing of surfaces of ICs or liquid crystal display devices in a semiconductor producing apparatus, used is a bellows type pump in which no particles are generated as a result of the pumping operation (for example, Japanese Patent Application Laying-Open No. 3-179184). In a pump of this kind, pulsations are produced by reciprocal motion due to extension and contraction of the bellows. In order to reduce the pulsations, therefore, also an accumulator is used (for example, Japanese Patent Application Laying-Open No. 6-17752).
In such a pump having a bellows, or an accumulator, there arises no problem when chemical liquids or pure water are used as transported liquid. However, a problem is produced in the case where abrasive liquid containing slurry such as silica is used as a polishing solution for Chemical Mechanical Polishing (CMP) of a semiconductor wafer, a hard disk which is to be incorporated into a computer, and the like. Namely, ridge-like folds of a bellows are formed so as to elongate in a direction perpendicular to the axis of the bellows in the contracting state. In the case where liquid containing a material such as slurry which easily sediments is used, therefore, the sedimenting material collects and sets on the inner sides of the ridge-like folds of the bellows, thereby producing problems such as that the set material causes the bellows to be broken, and that, even in the case where the bellows is not broken, sedimentation collects and aggregates and the shape of particles of the sedimentation is changed from that of the initial stage, thereby adversely affecting polishing.
The invention has been conducted in order to solve the problems. It is an object of the invention to provide a fluid apparatus which has a bellows, which is configured by a pump or an accumulator, and in which, even in the case where transported liquid containing a sedimenting material such as slurry is used, the sedimenting material can be prevented from stagnating and collecting in an extending and contracting portion of the bellows.